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PPQS Flashcards

1
Q

Suggest whteher clf3 HAS polar bonds

A

YES
- F more electronegative
- d+ cl, d- f

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2
Q

electronegativity

A

ability of an atom to attract the electronS in a covalent bond

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3
Q

why do repeats?

A
  1. increase repeatability
  2. find anomalies AND DISCARD
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4
Q

atomic emission spectra provisde evidence for …

A

quantum shells

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5
Q

6 MARKS
Problems and improvements of collection over water(gas collected 2 low)

A
  1. gas escapes from apparatus. use airtight bung with gas syringe
  2. metal covered with an oxide. clean with abrasive BEFORE weighing
  3. mass of metal used too low. use a more PRECISE balance
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6
Q

shortest bond length in CH3OH

A

O-H as largest difference in electronegativity

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7
Q

hydrogen bond angle

A

ALWAYS 180
- 2 bonding pairs
- 0 lone pairs

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8
Q

trigonal bipyrmaidal angles

A
  • 5 bp, 0 lp
  • 90 and 120
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9
Q

explain why the positive charge is on the carbon atom shown

A

tertairy carbocation is more stable than a primary carbocation
because it has more positive inductive alkyl groups

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10
Q

importance of termination (2)

A
  • 2 free radicals join together
  • dont form any free radicals
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11
Q

describe what is meant by cracking (2)

A
  • use of high temperatures
  • to break large molcules into smaller molecules, ,and produce alkenes
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12
Q

why can propene form 2 possible products with HBr

A
  • asymmetric alkene
  • Br could join to c1 or c2
  • to form 1 bromo or 2 bromo propane
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13
Q

biggest hazard of alkanes

A

flamable

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14
Q

in combustion where must the u-tube go

A

BEFORE boiling tube w lime water; distinguishes water as a product of combustion rather than the limewater

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15
Q

why can hydrogen chloride gas not conduct electricity but HCl acid can

A

covalent bond in hydrogen chloride changes to an ionic bond in aqueous solution

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16
Q

pressure in pvnrt is in

A

PASCALS

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17
Q

EXPLAIN WHY METHANOL IS SOLUBLE IN WATER

A
  • hydrogen bonding between them both
  • of same strength
  • comparable to the strength of the bonding in either component on its own
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18
Q

why is NaCL soluble in water but not methanol

A
  • hydration of BOTH ions in water
  • but ionic bonding is stronger than bonding between ions and methanol
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19
Q

2 reasons why x is more electronegative

A
  • more protons
  • smaller atomic radius
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20
Q

despit ehaving polar bonds why is x not polar

A
  • symmetricak
  • BOND POLARITIES CANCEL
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21
Q

use mexwell boltzmann diagram to explain why the use of a catalyst increases the rate of decomposition of ammonia (3)

A
  • area under curve represents fraction of molecules with E>= Ea
  • area with Ea of catalyst is greater; more molecules have E>= Ea
  • more freqeunt successful collision
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22
Q

similarities (2) and differences (2) between pi and sigma bonds

A

SIMILARITIES:
- both include the overlap of orbitals
- both involve electrostatic attraction between a BONDING pair of electrons and positive nuclei
DIFFERENCES:
- pi = sideways overlap of orbitals
- sigma = direct end on overlap of atomic orbitals

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23
Q

explain maxwell boltzmann at high temp

A
  • peak shifts to the right and lower
  • at higher temperatures there are more particles with higher energy
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24
Q

why might reaction not happen as shown

A
  • might react with oxygen
  • unlikely for reactants to be in correct ratio
  • reaction must occur in a series of steps as too many particles reacting in equation
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25
Q

+- of chemical test vs infrared to show alcohol

A

+
cheaper
rapid
can be done in schools
-
CHEMICAL TEST NOT AS SENSITIVE

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26
Q

vol gas a bit higher at higher temp

A

gases expand when heated

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27
Q

why is the measurement of initial rate less accurate than max

A
  • difficult to judge where tangent should be drawn for 0
  • compared to other points on the line
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28
Q

why is a heterogeneous catalyst good for gas reactant

A

provides a surface for the reaction

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29
Q

why might uncertainty of someone else be hgiher with mass measurement

A

they used a smaller mass w same balance

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30
Q

why does catalyst not effect amount of product made

A

increases rate of forward and backward reactions

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31
Q

why is catalyst heated and why might it melt

A
  • heated to provide activation energy
  • metls as bonds broken
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32
Q

advatnage of catalyst iN INDUSTRY

A
  • decreases activation energy
  • allows milder conditions to be used (lowering cost)
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33
Q

chromate (VI) ion colour

A

YELLOW

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34
Q

WHY IS ice less dense than water

A
  • water molecules in a lattice
  • molecules further apart in ice than water
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35
Q

TMS purpose

A

reference peak to compare other shifts to

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36
Q

what does NMR actually do

A

change spin state of hydrogen nuckeus

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37
Q

effect of increasing temp on rate constant

A

increases

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38
Q

why is there at least 2 steps (RDS REFERENCE)

A
  • x and y in RDS (z not in)
  • but more reactants in full equation
  • so must be another step containing z
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39
Q

why is the major product from the tertiary carbocation

A
  • most stable
  • inductive effect of alkyl groups
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40
Q

why are the other reactant concnetrations in hUGE excess in iodine clock reaction

A
  • concentration remain constant
  • so that [I2] is limiting reagent; only its concnetration changes
    -OTHERWISE A CURVE IS OBTAINED AS FULL ORDER OF REACTION
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41
Q

how to measure order of propanone as 1st order after already doing one step of iodine

A
  • doulbe conc of propanone
  • rate should double (gradient doubkes)
    OR
  • measure conc propanone over time
    -constant half life
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42
Q

how to quench iodine TITRATION

A
  • add NAHCO3
  • neutralizes acid
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43
Q

sodium hydrogencarbonate neutralising ACID catalyst ionic equation

A

HCO3- + H+ = H2O + CO2

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44
Q

why is mols of soidum thiosulfate v low

A
  • so concentration of reactants doesnt fall significantly before end point reached
  • used up during initial rate period
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45
Q

quenching with IODINE CLOCK method

A
  • take samples at various times
  • quench with ice
  • titrate using alkali
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46
Q

why might u get anomalies where rate is too high

A
  • rate is too high
  • reaction exothermic
  • more collisions with E>= Ea
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47
Q

what happens if no thiosulfate added in iodine clock

A

reaction goes blue black immediately

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48
Q

purpose of thiosulfate

A
  • as soon as iodide reacts to form iodine, thio reacts to turns it back to iodide
  • to prevents colour change occuring until a set amuont of reaction occured
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49
Q

how to use colorimetry for iodoine(3)

A
  • colorimetry
  • measure absorbance
  • CALIBRATION CURVE to turn it into concentration. absorbance proprotional to concentration
50
Q

biggest alkane hazard

A

TOXIC BY INHALATION

51
Q

reforming defition

A

converting straight chain HC to a ring/branched

52
Q

cracking defintion

A

breaking a longer HC to shorter chain HC

53
Q

describe waht happens to pi and sigma bonds in addition

A
  • pi bond breaks
  • sigma bond remains
  • as pi weaker
  • forms a carbocation intermediate
54
Q

alkene with acidificed potassium manganate (7)

A

DILUTE SULFURIC ACID
- forms a DIOL
- purple to colourless

55
Q

a fuel is …

A

a substance that produces energy

56
Q

why might the fuels be liquified

A

easier to transport

57
Q

hazard vs risk

A

hazard: potential to do harm
risk: likelihood harm will result

58
Q

which o the 2 ions has POLARIZING ability

A

cation

59
Q

formation of acid rain rain on limestone

A

REACTS with limestone to corrode buildings

60
Q

why conducgtivity different (ionic compounds)

A

cations are diff sizes

61
Q

why cant silicon conduct electricity

A
  • outer electorns FIXED in covalent bonds
  • no delocalised electrons
62
Q

why are polymers not sustainable

A

made from crude oil which is non-reneweable

63
Q

why is pi weaker than sigma

A
  • sigma direct end on overlap of orbitas- along line in between the 2 nuclei
  • pi = sideways overlap
64
Q

why is ice less dense than water

A
  • molecules spread out further apart
  • in a lattice
  • h bonds longer than covalent bonds
65
Q

why non polar insoluble n water

A

cant h bond with water

66
Q

ionic compounds solubility

A
  • soluble in water, ions hydrated
  • enthalpy change of hydration compensates for energy needed to break part lattice
  • INSOLUBE in non polar as any forces that would form between ion and substance weaker than ionic bondng
67
Q

describe the structure of. metal (3)

A
  • lattice
  • positive metal cations in layer
  • sea of delocalised electrons
68
Q

electrolyss of CuCrO4

A
  • ions migrate
  • Cu2+ blue colour towards cathode
  • CrO4 2- yellow colour towards anode
69
Q

2 sources of repulsion in ionic lattice

A
  • ions of same charge repel
  • positive nuclei repel
70
Q

purpose of reforming

A
  • more efficient combustion
  • fuels with a higher octane number
  • NO KNOCKING
71
Q

why might volume co2 be slightly lower

A
  • sligthyl soluble in water
72
Q

using a smaller cylinder multiple times vs a bigger one once

A
  1. look at error/ncertainty
  2. more time taken to refill loads
  3. GREATER TRANSFER LOSSES
73
Q

why does distillation work

A
  • difference in bp
  • the one with lower bp boils and vaporises first, so can be condensed and then collected
74
Q

purpose of reflux

A
  • reactants vapourise, then condense
  • return to reaction mixture
  • allows to reach BP without LOSS OF REACTANT
75
Q

HOW TO DISTILLATE TO GET PURE PRODUCT

A
  1. heat
  2. collect distillate
  3. at BP of the prducrt
76
Q

c-c with bromine vs c=c

A
  1. c-c sigma only
  2. strong bond, need to break c-h aswell
  3. c=c sigma and pi
  4. e- desnity above and below plane, polarises br-br
  5. pi bond weaker so easier to break
77
Q

2 conditions for cracking

A
  1. high temp
  2. silica catalyst
78
Q

conditions for haloalkane and ammonia and why

A
  • heat in a sealed vessel
  • increases pressure to increase rate of reaction]
  • but prevents loss of product
79
Q

purpose of needing ethanol with the water and AgNO3 for haloalkane test

A
  • cosolvent
  • dissolves both haloalkane AND water
80
Q

BP 2 chloro 2 methyl propane

A

50-52

81
Q

rate of hydrolysis primary, secondary, tertiary

A

primary slowest

82
Q

orbital

A
  • a region where there is a high probaility of finding electrons
  • holds up to 2 electrons with opposite spins
83
Q

explain why 1st electron affinity is negative but second is positive

A
  1. negative as exothermic due to attraction between POSTIIVE nucleus and electron
  2. postivie as endothermic as energy required to overcome
  3. repulsion between negative ion and electron
84
Q

assumptions for theoretiacl lattice energy (2)

A
  • 100% ionic bonding
  • ions are perfect spheres
85
Q

final comment for the theoretical lattice energy questions

A
  • more energy released when making the bond, so bond is stronger, and LE more exothermic
86
Q

2 problems with free radical substitution

A
  1. cant control number of cl that will substiutte; oversubstitution
  2. mixture of products will form, need to separate
87
Q

) Explain why benzene is resistant to bromination but ethene reacts readily
with bromine at room temperature.

A
  1. ethene c=c, electron density localised
  2. electron density delocalised in pi structure of benzene
  3. high ea for benzene as energy needed to break structure
  4. ethene more susceptible to electrophilic attack
88
Q

length hydrogen bonds compared to covalent

A

LONGER

89
Q

BIGGEST DIFFERENCE BETWEEN ACID HYDROLYSIS OF ESTER AND ALKALI

A

acid: acid is catalyst
alkali: alkali is a REACTANT

90
Q

why are condensation polymers biodegradable

A

ESTSER link can be hydrolysed by enzymes

91
Q

temperature conditions for nitration of benzene and why

A
  • below 55
  • PREVENTS MULTIPLE SUBSTITUTIONS
92
Q

Why is organic synthesis with less steps more eco frendly

A

higher yield

93
Q

reaction to form no2 + for nitration of benzene

A

HNO3 + 2H2SO4 = 2HSO4- + NO2+ + H3O +

94
Q

if Kp is x^2/y, discuss effect of incrasing pressure

A
  • increases partial pressure of numerator more than denominator as squared
  • so the mole fraction of y increases
  • to resotre Kp
95
Q

why hard to measure temp endo

A

difficult to measure temperature whilst heating

96
Q

describe what happens when copper sulfate dissolves in water

A
  • ionic lattice broken
  • water hydrates each ion
97
Q

why is HF boiling point the most

A
  • F is MOST ELECTRONEGATIVE ELEMENT
  • So stronger hydrogen bond
98
Q

2 problems with NOx that arent ghg

A
  • dissolve in water to form acid rain
  • breathing problems
99
Q

bond angle ice and water

A

different

100
Q

eg Kc is 1
there are more moles of products than reactants explain

A
  1. calculat new Kc; Kc >1
  2. moles products must decrease AND moles reactants must increase to restore Kc
  3. POE shifts to the left
101
Q

test for halide

A

HNO3
AgNO3

102
Q

WHAT SHAPE IS CATALYTIC CONVERTER AND WHY

A
  • honeycomb
  • increases SA
  • allows gases to flow through
103
Q

why cant distillation make ethanioc acid

A
  • ethanol oxidised to ethanal
  • low bp, distilled of as soon as formed
  • before full oxidation to ethanoic acid
104
Q

why would rate of reaction with oxygen decrease in a sealed vessel

A

concentration of oxygen decreases

105
Q

ratio of 35 Cl 2 , 35Cl37Cl, 37Cl2

A

9:6:1

106
Q

which apparatus for oxidation to ketone

A
  • reflux
  • to ensue full oxidation
107
Q

why might a temperature reading be wrong

A
  • mixture not stirred so temperature not unifor
108
Q

who burns wiwth a sooty flame

A

greater c:h
eg alkenes

109
Q

what does having a methyl group on the benzene ring do

A

INCREASE electron density
- positive inductive effect

110
Q

if organic synthesis q, increase carbon chain how?

A
  • if x1 : CN
  • if loads: polymer
  • if by a specific number of C : GRIGNARD
111
Q

in complete oxidation the oxidising agent is

A

in excess

112
Q

why might you get Cl 36 in mass spec

A

[35Cl37Cl]2+
m/z 36

113
Q

steps of recrytallisation

A
  • dissolve impure in MINIMUM volume of hot solvent
  • filter it hot through a preheated funnel
  • cool in ice bath + stir with glass rod
  • vaccum filtration (buchner filtration)
  • RINSE WITH ICE COLD ETHANOL
  • dry between filter paper
114
Q

distillation vs separating funnel

A

distillation: difference in BOILING POINTS
separating funnel: immiscible liquids

115
Q

if one H+ is used in the reaction but 2 are produced, can it still be a catalyst?

A

YES
- One is regenerated, so thats the catalyst
- one is a product of the reaction

116
Q

recrystallisation: why cool in ice bath

A
  • product is less soluble in colder solutions so will crystallise out
117
Q

recrystallisation: why warm filtering

A
  • to prevent crystallisation
  • which would reduce yeild
118
Q

recrystallisation: why buchner filtration

A
  • removes remaining solution (soluble impuirities) faster
  • dryer crystals
119
Q

problem if you have impurities in a gaseous reaction with a heterogeneous catalyst (3)

A
  • impurities ADSORB onto surface of catalyst, occupying active sites
  • fewer active sites avilable for reactants to adsorb
  • IMPURITIES LESS LIKELY TO DESORB
120
Q

purpose of TMS

A
  • calibration
  • to compare other hydrogen shifts
121
Q

explain why you can get pcl5 but not ncl5

A
  • PCl 5 can expand its octet
  • NCl5 cannot as no d orbital

chem (21 decks)

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